Ofcom estimates that up to 900,000 homes could be affected by interference in their TV signal.

This is because the 800Mhz band previously used for analogue TV was auctioned off for 4G. It's proximity to the 700Mhz band currently used for digital terrestrial TV (Freeview) is expected to cause disruption for some households.

Everything Everywhere, the joint venture of Orange and T-Mobile, launched 4G mobile last year, but using different spectrum to that sold in the Ofcom auction.

The full launch of 4G, which can deliver mobile internet speeds more than five times faster than 3G, will go ahead in the summer

at800 intends to produce maps showing the areas most likely to be affected by Freeview interference.

Most affected households will be able to address the problem by fitting a special filter that blocks the 4G frequency.

Filters will be supplied free of charge by at800, and vulnerable people will be able to get an engineer to fit one for them.

The Digital Television Group has been awarded the contract to test all at800 filters in its labs.

It will provide all conformance testing for manufacturers looking to supply filters authorised with the at800 logo.

DTG Testing associate director Richard Carlton said that 4G will bring faster mobile internet services, but also disruption for some Freeview users.

"We've been investigating coexistence issues between Freeview and 4G services at our Wireless Test and Innovation Centre to help inform the industry in advance of potential issues that may arise from the introduction of 4G services," he said.

"By applying this knowledge, combined with a decade of experience defining and conducting test and conformance regimes for digital terrestrial television, we can help at800 ensure that viewers at risk from interference are adequately protected."

at800 boss Simon Beresford-Wylie added: "Using a trusted body such as DTG Testing to ensure conformance of the filters we supply is an important step.

"It allows householders, professional installers and the retail industry to be confident that filters with the at800 logo meet the parameters required to mitigate interference of 4G services at 800 MHz."